Modern communication systems are becoming increasingly characterized by the networking of different technologies, transmission methods and transmission media. In non-homogeneous communication systems such as these, the transmission quality—and, in particular, the quality of voice transmission—is influenced to a significant degree by the particular communication network technology used, the transmission conditions in specific networks (e.g. in radio networks), or by handovers between different communication networks. Often, connections are fed at least partially via mobile radio networks with relatively low bandwidth and correspondingly poor voice transmission quality. In conference systems in particular, such differences in voice transmission quality in non-homogeneous communication systems can greatly diminish the intelligibility and distinguishability of conference participants.